1. Field of the Invention
The present invention relates to a hydraulic shock absorber for a vehicle. The hydraulic shock absorber according to the invention having significant, tuning and maintenance efficiencies.
2. Description of the Related Art
As a hydraulic shock absorber, as described in Japanese Patent Application Laid-Open (JP-A) No. 56-82680 (patent document 1), there is a structure in which an inner tube in an axle side is slidably inserted into an outer tube in a vehicle body side, a partition wall member is provided in an inner periphery of the inner tube, a working fluid chamber is comparted under the partition wall member, an oil reservoir chamber is comparted over the partition wall member, a piston supporting member attached to the outer tube side is inserted into the working fluid chamber through the partition wall member, and a piston sliding within the working fluid chamber is provided in a leading end portion of the piston supporting member. In this hydraulic shock absorber, a main suspension spring is interposed between an upper spring bearing in the piston supporting member side attached to the outer tube side and a lower spring hearing in a bottom portion, side of the inner tube, within the working fluid chamber of the inner tube.
The following disadvantages exist in the hydraulic shock absorber described in the patent document 1.
(1) To change a spring constant of the suspension spring, it is necessary to detach a partition wall member provided in an upper end portion of the inner tube and draw off the piston supporting member from the working fluid chamber in the inner tube in addition to detaching a cap from an upper end portion of the outer tube, in order to replace the suspension spring. Accordingly, many man hours are required.
(2) If the suspension spring is soaked into the working fluid chamber of the inner tube during replacement of the suspension spring; an oil amount is largely reduced in the working fluid chamber, because a coil diameter and a wire diameter of the suspension spring are thick and a surface area thereof is large. Accordingly, it is necessary to adjust the oil amount each time when the spring is replaced.
(3) If the suspension spring inserted to the working fluid chamber of the inner tube is replaced, an oil flow path flowing through a space between coils of the suspension spring is changed in an inner portion of the working fluid chamber, and a change of a damping force characteristic is generated.